1. Field of the Invention
The field of art to which this invention pertains is the recovery of vapors from gas-vapor mixtures. It particularly relates to the purification and recovery of desired vaporous constituents from feeds composed of vapors contaminated with undesirable gases.
2. Prior Art
Materials which are vaporous at normal conditions are employed in the synthesis of many chemical and petrochemical compounds. Ethylene, for example, is in demand as a starting material in the synthesis of alcohols and synthetic rubber. Propylene and butylenes are in particularly great demand for plastics manufacture and for conversion to high octane motor fuel blending components by polymerization and alkylation processes. Alcohols such as ethanol, propanol and butanol are also of paramount interest. Propane and butane are used extensively as LPG fuel.
Sources of these vaporous materials include such conversion processes as thermal cracking, catalytic cracking, reforming, hydrotreating, fermentation, hydrocracking, etc. The chemical reactions occurring in these processes produce commercially desirable quantities of vaporous materials, and because of their utility it is desirable to recover them in as high a concentration as possible. Unfotunately, these vapors are frequently contaminated by unwanted gaseous materials. In the case of LPG fuel, for example, the useful propane and butane vapors produced in a conversion process are frequently contaminated by hydrogen sulfide gas. For this reason, gas-vapor separation processes are commonly used to concentrate and recover these desirable vapors.
Gas-vapor separation processes currently in use are commonly comprised of two major sections or zones: absorption and stripping. In essence, these zones serve, respectively, to absorb all but the lightest gaseous components and to strip dissolved gases from the absorbed components so that gases are removed from the desired vapors. The major disadvantage of such prior art purification processes is their high energy consumption. I have discovered a process for vapor purification which by virtue of its lower energy consumption is an improvement over prior art processes.